Atomizing nozzle an filter and spray generating device

ABSTRACT

A nozzle assembly for use in atomizing and generating sprays from a fluid. The nozzle assembly includes two members, each with generally planar surfaces, that are joined together. A first set of channels is formed in the generally planar surface of a first one of the members to form, in cooperation with the generally planar surface of the second of the members, a plurality of filter passageways. A plenum chamber is formed in the first member. The plenum chamber is in fluid communication with and downstream of the plurality of filter passageways. A second set of channels is formed in the generally planar surface of the first member to form, in cooperation with the generally planar surface of the second member, a plurality of nozzle outlet passageways. These nozzle outlet passageways are in fluid communication with the plenum chamber. The nozzle outlet passageways include a plurality of nozzle outlets which are adapted to discharge a plurality of fluid jets that impinge on one another to thereby atomize a flow of fluid.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of Appl. Ser. No. 09/303,670,filed May 3, 1999, allowed now U.S. Pat. No. 6,007,676, which is acontinuation of Appl. Ser. No. 08/661,741, filed Jun. 11, 1996, now U.S.Pat. No. 5,911,851, which is a continuation of Appl. Ser. No.08/462,680, filed Jun. 5, 1995, now U.S. Pat. No. 5,547,094, which is adivision of Appl. Ser. No. 08/128,021, filed Sep. 29, 1993, now U.S.Pat. No. 5,472,143.

BACKGROUND TO THE INVENTION

1. Field of the Invention

The present invention relates to an atomising nozzle and to such anozzle with a filter, notably to one which produces a spray of finedroplets suitable, for example, for the administration of a medicamentby inhalation, to the production of such nozzles, and to aspray-generating device incorporating such nozzles.

2. Description of the Prior Art

It is known (e.g. from WO 91/14468) that fluids can be caused to formvery fine droplets on being forced through narrow nozzles at highpressure. WO 91/14468 proposes to manufacture the necessary nozzlesusing methods such as those known in the manufacture of spinningnozzles. These nozzles are produced, for example, by boring through athin metal plate with a tungsten-carbide. An important area ofapplication for the equipment according to WO 91/14468 is the productionof aerosols for inhalation therapy. Demanding requirements are imposedamong other things, on the fineness of the droplets; it has been foundduring numerous investigations that a considerable number of dropletsmust have a size less than 6 μm in order that a sufficient quantity ofthe medicine can reach deep enough into the lungs. For safe treatmentthe individual pieces of equipment must each produce the same dropletspectra, since only then is it certain that the given dose of themedicine will be delivered to the lungs in the desired way.

With the mechanical production of nozzles there are sometimes disturbingdeviations from nozzle to nozzle, possibly due to the walls of thenozzles being of varying degrees of roughness. It is, amongst otherthings, difficult to produce double nozzles, like those shown in FIG. 8of the afore-mentioned WO 91/14468, with the necessary accuracy. Inaddition, it is not an easy matter to obtain nozzles of changingcross-section using known methods. possibly with a view to acceleratingor slowing down the flow of fluid in the nozzle, or to provide impactelements or vortex-generating devices.

In PCT Application No GB91/00433, there have been described methods anddevices for forming sprays of fine droplets from a fluid without the useof pressurised propellant gasses, notably for the formation of sprays ofa fluid medicament which have a mean droplet size of less than 10micrometres for inhalation by a user so that the droplets of medicamentcan penetrate into the lower lung. In PCT Application No GB91/02145,there have been described methods and devices by which the formation ofsuch sprays can be optimised by inducing secondary flows in the streamof fluid when it passes through the nozzle aperture.

In the preferred form of such methods and devices, a metered dose of thefluid medicament is drawn from a reservoir into a pressure chamber byretracting a piston in a cylinder of a pump mechanism against the actionof a drive spring. The piston or spring is latched or otherwise retainedin the retracted, or cocked, position so that the metered dose is heldat ambient pressure in the pressure chamber of the pump until it isdischarged. When discharge is required, the piston or spring is releasedand the spring drives the piston forward, thus applying a rapid pressurerise to the fluid causing it to discharge through the nozzle apertureand form a spray of droplets.

The very fine droplets required for the application of a medicament tothe lower lung are achieved by the use of fine aperture size nozzles andhigh pressures, typically with nozzle apertures of less than 20micrometres and pressures in excess of 300 bar.

The nozzle apertures required to achieve such fine droplets can beformed in a number of ways, for example by punching a hole in a metalplate and part closing up the hole to achieve a fine aperture with arough rim which causes the secondary flows in the fluid stream as itpasses through the nozzle aperture. However, the techniques used to formthe nozzle aperture either require accurate machining of components on amicroscopic scale, which is expensive and time consuming and does notgive consistent results, leading to rejection of components duringquality control assessment prior to use or to inconsistent operation ofthe device. Furthermore, the need to be capable of enduring the veryhigh pressure surge, possibly as high as 600 bar, when the device isactuated requires the use of mechanically strong components. Again thisadds to the cost of the device.

In PCT Application No GB91/02147 there has been described a form ofconstruction which incorporates an integral one way valve and filter inthe nozzle assembly to prevent air being sucked into the device throughthe discharge nozzle when the piston is being retracted to draw themetered dose of fluid from the reservoir and to prevent blockage of thefine nozzle aperture by solid particles entrained in the fluid. In apreferred form of such a construction a cylindrical plug is a push fitin a chamber immediately upstream of the nozzle orifice to provide anannular passage between the internal wall of the chamber and theradially outward wall of the plug. This annular passage has a radialdimension equal to or less than the nozzle aperture and thus provides afine filter to remove solid particles which might otherwise block thenozzle aperture. The fine annular passage also imposes a flow restrainton the movement of fluid which is overcome by the high pressuregenerated when the piston is driven on its forward, or discharge, stroketo allow fluid to flow outwardly through the nozzle aperture. The flowrestriction, however, prevents fluid from flowing back into the deviceas the piston is retracted. This reduces the risk of contamination ofthe fresh fluid drawn into the pressure chamber from the reservoir withair or fluid from the nozzle assembly downstream of the plug. Again sucha device must be manufactured from metal to be able to withstand thepressure surge as the device is operated and thus requires highprecision machining of components which is expensive.

SUMMARY OF THE INVENTION

An object of the invention, therefore, is to provide a device and amethod for the manufacture of a nozzle which reduces the above problemsand is capable of being made with a high degree of accuracy at low cost.

In accordance with one aspect of the invention, there is provided anozzle with one or more nozzle outlets for the atomisation of fluidsconsisting of at least two plates which are connected together, possiblyby an intermediate layer, wherein at least a, base plate has a groovedstructure which connects the intake side of the nozzle to the nozzleoutlet(s)

An embodiment of the invention can thus provide a nozzle (also referredto herein as a nozzle assembly) which is composed of two or more plates;at least one of which, a base plate, is formed with grooves which joinan intake side and atomiser nozzle outlets provided on an oppositelydisposed side, whilst another plate (the cover plate), which willnormally be unstructured, is placed upon the structured side of the baseplate and is joined firmly thereto. A nozzle assembly consisting ofthree layers can consist, for example, of a structured silicon plate, aflat silicon cover plate and a thin glass plate therebetween. Of coursethe functions of the base and cover plates can be reversed with astructured cover plate overlying an unstructured base plate.

The cavities in the nozzle assembly are usually of rectangularcross-section. However, a large number of variations is possible if thenozzle assembly is manufactured by way of the method describedhereinbelow and related methods known to those skilled in the art. Byusing different etching methods, it is also possible to produce baseplates with grooves of other cross-sections if so desired.

If the cover plate is structured in addition to the base plate, then itis possible to obtain other cross-sections, e.g. cross-sections ofapproximately circular shape. When both the base plates and cover platesare structured, both plates are usually given identical structures.Other variations are possible if the base plate and cover plate arestructured in different ways but adapted to cooperate with one another.

According to another aspect of the invention, there is provided a spraygenerating device comprising a nozzle assembly for forming the spray ofdroplets from a stream of fluid fed to it by a means for generating aflow of fluid which nozzle assembly comprises:

a. a first member having formed in a first face thereof one or morefluid inlet(s) adapted to feed fluid to one or more fluid outlet(s)located at an edge of the first member, the outlet(s) being configuredso that a spray of droplets is formed by the fluid outlet(s) from astream of fluid flowing through them;

b. a second member secured upon the said first face of the first memberand adapted to co-operate with the first member to provide one or moreconduits each adapted to connect a said fluid inlet in fluid flowcommunication with a said fluid outlet, preferably the said secondmember co-operates with one or more channels formed in the said firstface of the said first member to define the walls of one or more fluidconduits connecting said fluid inlet(s) to said fluid outlet(s); and

c. means for connecting said fluid inlet(s) to said means for generatingthe flow of fluid.

It is preferred that the fluid flow conduits each incorporate one ormore narrow bore portions which have transverse dimensions and atransverse cross-section which is less than that of the fluid outlet(s)and which act as filters to protect the outlet(s) against blockage bysolid particles in the fluid. The narrow bore portions also provide aflow restriction in the conduits which act as one way valves of the typedescribed in PCT Application No GB 91/02147.

Preferably the first member is a substantially planar member and thechannel(s), fluid inlet(s) and fluid outlet(s) are formed in a face ofsaid first member with the longitudinal axes of the channel(s) and ofthe inlet(s) substantially parallel to the plane of said face and theplane of the outlet aperture substantially normal (perpendicular) to theplane of the first member; and the said second member is a secondgenerally planar member which is preferably of substantially of the sameplanar shape and size as the first member.

The means for connecting the fluid conduits of said first member to theflow generating device is preferably provided by locating one or more ofthe fluid inlet(s) at an edge of the first or second members andproviding means by which the first and/or second members can bemechanically connected to the flow generating device, for example bybeing a sealed push fit into the fluid outlet of the flow generatingdevice. Alternatively, a third member can be provided which is securedto a second face of either the first or the second member and which isprovided with a fluid conduit adapted to be put in fluid flowcommunication with the means for generating the fluid flow. For examplethe third member can carry a spigot which is a push or other fit in theoutlet to a pump mechanism of the type described in PCT Application NoGB91/00433 and which has a bore which communicates with the fluidinlet(s) in the first member. The bore of the spigot can act as thecylinder of the pump mechanism in such a device.

A nozzle assembly in accordance with the invention can readily be formedas a laminated unitary construction from components which have had theappropriate channels, inlets and outlets pre-formed therein by laserchemical etching photo-resist or other surface engraving techniques wellknown in the micro-forming art to achieve simple but accuratelyreproducible components having substantially flat opposing faces. Thesecomponents can be secured together by diffusion bonding, adhesion,welding, clamping or other suitable techniques for securing themtogether in sealing engagement, optionally with sealing rings or othersealing interfaces between the members by simple assembly techniques.

In accordance with a further aspect of the invention, there is provideda nozzle assembly comprising:

a. a first member, which is preferably substantially planar, having oneor more fluid inlet(s) formed therein, one or more fluid outlet(s)formed at an edge of the said first member and preferably also one ormore channels formed in a first face of said first member substantiallyparallel to the plane of said face, the channel(s) connecting the fluidinlet(s) with the fluid outlet(s) in fluid flow communicationand-preferably incorporating one or more narrow bore portions which areadapted to act as filters and one way valves;

b. a second member, which is preferably substantially planar and ofsubstantially the same planar shape and size as the said first member,located upon said first face of said first member and co-operating withsaid first member to provide, and/or to define with the said channel(s)where present in said first member conduit(s) for connecting said fluidinlet(s) with said fluid outlet(s) in fluid flow communication; and

c. means for connecting the fluid inlet(s) of said first member in fluidflow communication with a means for generating the fluid flow.

Preferably, the fluid inlets, the fluid outlets and the connectingchannels are formed wholly in the first face of the first member and thesecond member is a cover member secured over said first face to providethe wall forming the conduits. However, the second member can beprovided with part or all of the connecting conduits as when the secondmember is provided with the channels and the first member provides theclosing wall for those channels. Similarly, the second member can beprovided with part of the inlets and/or outlets formed therein. Forexample, the first and second members can have mirror image halves ofthe inlets, outlets and conduits cut in the opposed faces thereofwhereby securing them together forms the desired whole inlets, outletsand conduits.

For convenience, the invention will be described hereinafter in terms ofa first member which has the whole depth of the inlets, outlets andchannels formed in the first face thereof and the second member has asubstantially flat face which provides a wall to complete the inlets,outlets and conduits.

The fluid outlet(s) act as the spray generating means of the nozzleassembly. These can therefore be simple fine bore orifices which canhave rough, polygonal or other cross-sections or edges, as described inPCT Application No GB 91/02145, to form a spray of droplets from astream of fluid passing through the outlet aperture. Thus, the aperturecan have a triangular, squared or other regular or irregular polygonalshape, preferably having a maximum to minimum aperture dimension of from1:1 to 10:1. The lip of the aperture can be rough, as when the apertureis formed by an electro-sputter erosion technique in which material isremoved from the first member by striking an arc between the member andan electrode. However, it is preferred that the aperture have a sharplip thereto over which the fluid flow changes direction sharply toachieve the secondary flow in the mainstream of the fluid flow.Typically the change in direction will be equivalent to at least 5%,preferably from 10 to 30%, of the total flow changing direction through90°. Preferably, the change in direction occurs sharply, notably withinan axial distance of less than five, preferably less than one, diametersof the width of the flow. Such change in direction, or secondary flow,can also be achieved by forming the aperture with an axially inwardlydirected lip as opposed to an externally directed lip, for example wherethe aperture diverges along the line of flow and has an equilateraltriangular plan shape with its apex directed against the intended lineof flow of the fluid through the aperture. Alternatively, two channelscan intersect within the plan area of the first member to form aturbulent flow in a single channel leading to the fluid outlet aperturelocated at the edge of the first member.

Alternatively, the change in direction can be caused by forming a flapor partial obstruction to the aperture whereby at least part of the flowof fluid through the aperture is subjected to a sharp change indirection by the flap or obstruction. Such a flap or obstruction acts onfrom 10 to 80% of the effective cross-section of the flow. Other formsof secondary flow generators are described in PCT Application No GB91/02145 and the subject matter of that application is incorporatedherein by this reference.

Where the fluid outlet is formed so as to generate the spray by means ofthe secondary flow caused by the shape and configuration of the outlet,we have found that satisfactory sprays can be produced with flowgenerating devices which generate a pressure low as 25 bar wherecomparatively large droplets are required, for example from 30 to 150micrometres mass median droplet size. However, when droplets with a massmedian size of less than about 20 micrometres are required, it willusually be necessary to use a flow generating device which generates apressure of at least 50 bar, typically 100 to 400 bar.

The droplet size will also be affected by the nozzle aperture size.Thus, in general we have found that it is desirable to use apertureswith maximum transverse dimensions of less than 500 micrometres, forexample 50 micrometres or less. Where fine droplet sized sprays arerequired, the maximum transverse aperture dimension is preferably lessthan 30 micrometres. Such dimensions correspond to cross-sectional areasof from 5 to 2,500, eg. 10 to 500, square micrometres. Where coarsesprays are required, the aperture size can be to 100 micrometres maximumtransverse dimension

As indicated above, the desired spray can also be formed by causing twoor more jets of fluid to impinge upon one another or for a single jet,to impinge on a fixed impinger. In this case it is not necessary thatthe nozzle aperture cause any significant amount of secondary flow and asmooth lipped substantially circular, squared or rectangular aperturecan be used. In order to produce an acceptable jet, it is preferred touse a flow generating device which generates a fluid pressure of from 50to 400 bar and an aperture with a maximum transverse dimension of from 5to 100 micrometres. Where two impinging jets are used, it is preferredthat the line of flight of the jets include an angle of from 60 to 150°,preferably about 90 to 120°, at the point of impact and that the impactoccur from 25 to 500, eg. from 30 to 100, micrometres from the plane ofthe edge of the first member at which the fluid outlets are located.Where a jet of fluid strikes a fixed impinger, it is preferred that thisbe located in the line of flight of the jet at a point before the jetbegins to break up into separate droplets, typically less than 1000micrometres downstream of the fluid outlet and that the surface of theimpinger be angled to the line of flight of the jet so that the impingeris self cleaning and does not retain a significant amount of fluidthereon. A suitable form of such a self cleaning impinger is describedin PCT Application No CB 92/0668.

Embodiments of the invention are described hereinafter in terms of theuse of two fluid outlets to form twin jets of fluid which impinge uponone another to form a spray of droplets.

The fluid outlets are fed with fluid under pressure from the fluid flowgenerating means via the fluid inlet and the conduits formed in thefirst member. The fluid inlet is conveniently provided by a simplecircular or other shaped chamber in the first member which is in directfluid flow communication with the flow generating device via inlets atthe edge of the first member or via a spigot or other means by which thenozzle assembly is mounted on the flow generating device. As indicatedabove, this spigot can form part of the pump mechanism of the flowgenerating device and an be carried by a third planar member which ismounted on the opposed face of the first member to that carrying thesecond member However, the first member could be formed with the spigotformed integrally therewith, for example as a metal or other tubularprojection from the second face of the member.

Embodiments of the invention will also be described hereinafter where athird member carries the spigot protruding therefrom.

A single fluid inlet chamber in the first member typically receives allthe fluid fed to the nozzle assembly and distributes it to the fluidoutlet(s). If desired, the fluid inlet chamber can be elongated in oneor more directions to assist uniform flow of the fluid to the fluidoutlets. For convenience, the invention will be described hereinafter interms of a single generally circular inlet chamber.

The inlet feeds fluid via one or more conduits to the fluid outlet(s).As stated above, these conduits are formed by etching, engraving orotherwise forming suitable channels in the face of the first member, forexample by inserting fine wires or ablatable material filaments into theinterface between the first and second members so as to form depressionsin the opposed faces of the members and then removing or burning awaythe wires or filaments to form the channels and outlets. The channelswill typically have a generally squared cross-section since they are ingeneral formed by the removal of material uniformly across the wholewidth of the channel.

As stated above, it is particularly preferred than the channels have oneor more portions which are narrower than the aperture of the fluidoutlet so that these portions act as filters to prevent solid particleswhich might block the fluid outlets from reaching the outlet in a mannersimilar to the fine bore passages described in PCT Application No GB91/02147. Such a fine bore portion of the conduit preferably hascross-sectional dimensions which are from 10 to 80% of those of thefluid outlet. It is also preferred that the fine bore portion of thechannel cause a pressure drop of from at least 0.5 bar in the flow offluid through the portion of the channel so that the narrow bore portioninhibits withdrawal of fluid from the channel during retraction of anypump mechanism used to generate the flow of fluid through the nozzleassembly. Preferably, the pressure drop is the minimum required toprevent return flow of fluid and air from the nozzle to the flowgenerating device and yet does not deleteriously affect free flow of thepressurised fluid through the channels and the fluid outlet(s). Theoptimum flow restriction can readily be determined for any given case,but will usually achieve a pressure drop of from 1 to 3 bar or more.

While the channels may communicate directly with a fluid outlet, it ispreferred that the narrow bore portions of the channels be locatedbetween the fluid inlet and a plenum chamber which feeds fluid to thefluid outlets. Such a plenum chamber aids uniform distribution of theflow of the fluid to the outlets where more than one outlet is used, forexample where two outlets are used to form two jets of fluid whichimpinge upon one another. The plenum chamber may also be configured soas to assist the formation of secondary flow in the fluid as it flows tothe outlet(s), for example by incorporating curves or other wallconfigurations for causing swirling in the fluid flow.

The nozzle assembly finds use on a wide range of fluid flow generatingdevices, such as pressurised gas or aerosol type dispensers in whichfluid is caused to flow out of a container by the expansion of apropellant gas. However, the nozzle assembly is of especial applicationin forming a spray from a flow of fluid generated by a manually operatedpump mechanism, thus avoiding the use of a propellant gas. The pumpmechanism may be of the type described in PCT Application NO GB91/00433. The nozzle assembly is mounted by any suitable means upon theoutlet from the pressure chamber of the pump, for example by a screw,bayonet, push or other fit, and receives the metered dose of the fluidwhen the spring or other energy source is released and the pressurewithin the pressure chamber rises. Other forms of fluid flow generatormay also be used, provided that they can achieve the required pressurerise to discharge the fluid through the fluid outlet(s) as a spray withthe desired mass median droplet size.

As indicated above, the channels, the fluid inlet the plenum chamber andthe fluid outlets are all formed in one face of the first member,although the fluid inlet can extend through the thickness of the firstmember to communicate with the fluid flow generating means. Such adesign readily lends itself to fabrication by selectively removing thenecessary material from the required areas of the surface of the firstmember by etching or engraving techniques which can be accuratelycontrolled to form the very fine features required for the presentinvention. Such techniques are known and used in the formation ofchannels and nozzle outlets in the manufacture of ink jet printer heads,see for example US Patent 4915718 and European Application No 0397441,and in general comprise the application of a mask to a photo-resist orchemically etchable material; sensitizing the material and removing thematerial in the required areas by application of a suitable etchingmaterial. Alternatively, the channels can be formed by burning away thematerial using a laser or by striking an arc between the member and anelectrode. Other methods for forming the features on the surface of thefirst member may be used for example milling or fine engraving ofsilicon, ceramic or metal plates.

Such techniques can be used to remove accurately controlled amounts ofmaterial from accurately defined selective areas of the surface of thefirst member to form, within reason, any desired shape of channel, fluidoutlet or other feature. Such techniques are especially applicable toplanar surfaces and it is therefore preferred that the surface of thefirst member in which the features are to be formed is substantiallyflat. However, they may also be applied to curved or irregular surfacesso that the surface of the first member need not be flat if desired.

The components of the nozzle assembly for use in the present inventionthus readily lend themselves to manufacture by such techniques from awide range of materials which are conventionally used in suchtechniques, for example photo-resist plastic, silicon, ceramics, metals.Such materials can be produced to a high degree of accuracy and areoften strong enough to resist the stresses due to the high pressurerises imposed upon the nozzle assemblies without the need for supportingframework or other structures. Furthermore, being substantially flatmembers the first, second and third members can readily be secured toone another in sealing engagement. Thus, metal, silicon or ceramicplates can readily be bonded together by pressure welding or bydiffusion bonding in which an interface of a suitable metal, for examplegold, is located between the opposed faces of the member and bondingcaused by the application of heat and pressure. Such diffusion bondinghas the advantage that little distortion of the shape of the channelsand other features in the face of the first member is caused, thuspreserving the accuracy of the features once formed.

Alternatively, the first and second members of the nozzle assembly canbe secured in position by the use of adhesives, conventional ultra-sonicor other welding techniques or by mechanically clamping the componentstogether. If desired, sealing rings or gaskets can be located betweenthe opposing faces to ensure a fluid tight seal. However, where thefaces of the members are sufficiently flat, this will usually not benecessary and the adhesive or metal diffusion interface between theopposed faces will ensure an adequate seal.

If desired, the assembled nozzle assembly can be located within asupporting housing or the like to impart the necessary strength to theassembly to withstand the high pressures generated by the devices of ourPCT Application NO GB91/00433.

In particular, the nozzle assemblies according to the invention arepreferably manufactured by means of the following steps:

structuring a batch of base plates with grooves;

joining the base plates and cover plates; and

separating the individual nozzle assemblies. The

grooved finish is preferably produced simultaneously for a plurality ofnozzle assemblies over a large surface area in a parallel manufacturingprocess, and then the base and cover plates are joined in one step (i.e.a batch process). Thereafter, the composite structure is divided intoindividual tiles or chips, and the inlet and outlet openings of thenozzle assemblies are opened up.

There are special advantages with this type of manufacture. The batchmanufacture first of all makes it possible to produce individualcomponent parts which are particularly cheap, and which could only beproduced using serial processing methods at considerably greaterexpense. The batch manufacture secondly guarantees a specific constantquality for all parts which can be reproduced repeatedly under the sameprocessing conditions, a quality which is never subject to gradualchange, as would be the case in serial processing methods due to wear ofthe worktool(s).

Also, the position and placement of the parts in the process aredetermined likewise by the overall design, and does not therefore haveto be altered by time-consuming sorting- or handling machines.

Thus, the present invention relates to new, highly effective nozzleassemblies and methods which can be used to produce large numbers ofthese nozzle assemblies so that they are of constant high quality; inaddition, a filter—possibly a multi-staged filter can be integrated inthe nozzle assembly.

The materials and methods which can be used according to the inventionproduce nozzles which excel through a number of advantages:

high mechanical stability;

a high degree of resistance to chemical influences (e.g. aqueousmedicine solutions, acids);

low surface roughness of the grooves;

low influence of larger pressure- and temperature differences;

valve function of the nozzle members filled with fluid with lowerpressures.

The nozzle assemblies according to the invention can be very small insize, so that the dead volume is very small, and therefore when thenozzle members are used in the therapeutic domain (production ofinhalation aerosols) the dead volume accounts for only a small fractionof the quantity of fluid to be diffuse.

Surprisingly, the provision of shallow grooves means that no problemsresult with transportation of the fluid, despite the fact that smallflow cross-sections are likely to give problems with the boundarylayers.

The nozzle assembly of the invention thus offers a simplified designwhich does not required expensive and time consuming machining ofcomponents and which enables components to be made reproducibly to ahigh degree of accuracy and which can readily be assembled to form thenozzle assembly.

The invention also provides a method for producing a nozzle assembly foruse in a spray generating device of the invention, wherein the fluidoutlet(s), the fluid inlet(s) and the connecting channels are formed inthe face of the first member by selectively removing material from thatface; and securing a second member upon the said first member wherebythe face of said second member opposed to said first member co-operateswith the said fluid outlet(s), fluid inlet(s) and said channels to formthe fluid flow paths for said nozzle assembly.

DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail hereinafter, by way ofexample only, in terms of a number of exemplary embodiments withreference to the accompanying drawings, in which:

FIG. 1 is a schematic perspective view of a preferred embodiment of anozzle assembly in accordance with the invention and

FIG. 1A is a detail of a possible variant of a nozzle outlet for theassembly of FIG. 1;

FIG. 2 is a schematic plan view of part of a second preferred embodimentof a nozzle assembly in accordance with the invention, FIGS. 2A and 2Brelating to details thereof;

FIG. 3 is a schematic plan view of part of a third preferred embodimentof a nozzle assembly in accordance with the invention employing twinnozzle outlets, FIGS. 3A and 3B relating to details of that nozzleassembly;

FIGS. 4, 4A, FIGS. 5, 5A, FIGS. 6, 6A and FIGS. 7, 7A relate to specificexamples of twin nozzle outlets for a nozzle assembly in accordance withthe invention;

FIG. 8A relates to a detail of a nozzle assembly comprising a pluralityof nozzle outlets;

FIG. 9 relates to a detail of a nozzle assembly employing a nozzleoutlet with an impinging element;

FIG. 10 and FIGS. 11A, 11B, and 11C relate to alternative designs for anozzle outlet for use in a nozzle assembly in accordance with theinvention;

FIG. 12 is a schematic plan view of part of a nozzle assembly inaccordance with a further embodiment of the invention;

FIG. 13 is a schematic plan view of yet a further alternative embodimentof a nozzle assembly in accordance with the invention;

FIGS. 14, 15, 16, 17, 18 and 19 relate to yet further examples of nozzleoutlet designs for a nozzle assembly in accordance with the invention;and

FIGS. 20A, 20B, 20C, 20D, 20E, 20F, and 20G represent various stages inthe manufacture of a nozzle assembly in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic exploded perspective view from above of an exampleof a nozzle assembly 10, or of part thereof, in accordance with theinvention.

FIG. 1 shows a base plate 11 and a cover plate 12, which has been liftedoff the base plate 11 for illustrative purposes. In use, with the covermounted on the base plate 11, fluid is passed under pressure through afilter 13 at an intake side 16 of the nozzle assembly 10, which filteris composed of a number of mutually parallel narrow grooves 17, thecross-section of each groove 17 of which should be less than thecross-section of a nozzle outlet 14. From the filter 13, the fluidpasses under pressure into the channels 15, from where it is expelledthrough the nozzle outlet 14.

FIG. 1a shows a variant of the grooved plate 11, in which the nozzle 14is bent, and instead of two channels 15 which extend at an obtuse anglerelative to each other as in FIG. 1, a series of parallel channels 15 isprovided.

FIG. 2 shows another version of a nozzle assembly 20 in accordance withthe invention. This drawing shows a view from above onto a grooved plate21, where—as seen from the intake side 26—a coarser filter 23 withgrooves 27 is followed by a finer filter 28, which is shown in a cut-outsectional drawing on a larger scale in FIG. 2a. The filter 28communicates with the nozzle outlet 24 via channels 25. The right anglesdisposed between the channels support the cover plate (not shown) andreinforce its connection to the grooved plate 21.

It has been found that in the case of individual nozzles outlets likethose in FIGS. 1 and 2, more favourable droplet spectra can be producedif the nozzles 14 and 24 are short in the flow direction. If twinnozzles outlets (see for example FIG. 3) are provided, longer (e.g.conical or tapering) nozzles can give good atomization results becausethe fluid jets are split into the finest droplets when they collide.

FIG. 3 shows part of a nozzle assembly 36 in which the two-stage filter37, 38 and the five parallel channels 35 generally correspond to thefilter 27, 28 and channels 25 of the embodiment shown in FIGS. 2/2 a.The nozzle outlet 24 according to FIG. 2 is, however, replaced here bythe twin nozzle outlet 39 a/39 b. As can be seen from the enlargeddrawing in FIG. 3b, the twin nozzle outlets 39 a/39 b direct two jets atan angle of 90° relative to each other. Due to the collision of thejets, particularly good atomization is obtained. The twin nozzle outletscan be modified in various ways. Thus, both jets can, if so desired, beoriented towards each other at a more acute angle or at a more obtuseangle (about 20° to 160°, preferably 60° to 150° and more preferably 90°to 120°). In addition the cross-section of the nozzle outlets can beselected differently; for example the strong tapering of the outlets 39a/39 b in FIGS. 3, 3 a, may be dispensed with. As illustrated in FIG.3b, it is desirable for the jets to impinge a slight distance away fromthe nozzle outlets. Smaller orientation deviations do not then result inincomplete collision of the jets on one another. The edges of thestructure may be bevelled where long term use of the channel plate mightcause breakages to the edges which could cause the filter or nozzle tobecome blocked.

FIGS. 4, 5, 6 and 7 represent plan views of alternative configurationsof a twin nozzle outlet. Each of these Figures shows the nozzle outletregion only of one plate of a nozzle assembly. For illustrativepurposes, a filter arrangement and the channels for the passage of fluidfrom the filter arrangement are not shown in FIGS. 4 to 7. The filterarrangement and channels may be configured either as shown in FIG. 1, orin FIGS. 2/3, or another suitable manner The shaded areas representedraised portions of the grooved plate 21 with the portions not shadedrepresenting the grooved or recessed areas.

FIGS. 4A, 5A, 6A and 7A represent enlarged views of the nozzle outletarea of the grooved plates 314, 315, 316 and 317 shown respectively, inFIGS. 4, 5, 6 and 7. The dimensions shown in FIGS. 4/4A, 5/5A, 6/6A and7/7A are in millimetres. The depth of the grooved (i.e. non-crosshatched) portions is 0.005 mm below that of the hatched areas in thosedrawings.

In FIG. 4A, each nozzle outlet portion 394 a/394 b has a length of 0.04mm and a constant breadth of 0.008 mm. As stated before, the depth ofthe nozzle outlet is 0.005 mm. The central island 391 has a radius of0.1122 mm. The nozzle outlets are arranged so that the fluid jets exitthe nozzle outlets at 90° with respect to each other and collide at0.025 mm from the outlet surface 398 of the nozzle assembly.

In FIG. 5A, the outlet nozzles are shown to have a length of 0.08 mmwith a constant width (nozzle outlet portions 395 a/395 b) of 0.008 mm,and a depth, as before, of 0.005 mm. The nozzle outlets are configuredso that the fluid jets exit at 90° with respect to each other andcollide at a distance of 0.0025 mm from the outlet surface 398 of thenozzle assembly.

In FIG. 6A, the nozzles have the same configuration as in FIG. 5A, withnozzle outlet portions 396 a/396 b. However, in FIG. 6A, the islandportion 392 is configured differently from the island portion 391. Itwill be seen that the inner surface of the island portion 391 and alsothe inner surface of the outer wall regions 393 are configured to have aconcave radius of curvature of 0.2 mm.

In the arrangement shown in FIG. 7A, the outer wall and island portionsare configured similarly to those in FIG. 6A. Also, the overall nozzleoutlet configuration is similar to that in FIG. 6A, with the exceptionthat the nozzle outlets are arranged to be slightly tapered, having awidth of 0.007 mm at the inner end and a width of 0.008 mm at the outerend. This configuration is intended to facilitate the removal ofparticles through the nozzle should such particles pass the filtersshown in FIGS. 2/3 and reach and enter the nozzle outlet portions 397a/397 b.

FIG. 8 shows the nozzle outlet region of a nozzle assembly according tothe invention wherein six nozzle outlets 9 a to 9 f are oriented in sucha way that the jets which issue therefrom meet at a point. This canavoid a situation where the other jets no longer collide if one of thenozzles becomes blocked. In FIG. 9, an impact element 43 is provided inthe mouth 44 of a nozzle outlet 45, which widens towards the outside.Similarly, in FIG. 10, a vortex-generating structure 46 is fitted into amouth 47 of the nozzle outlet which promotes a greater vortex formationof the issuing fluid. FIGS. 11a to 11 c also show a section of thenozzle assembly in the region of the nozzle outlet, wherein variousgeometric shapes for the nozzle outlets are illustrated at 48 a, 48 band 48 c.

To improve the atomization, the nozzle outlet can also be designed insuch a way that it is somewhat longer and is provided with a region ofreduced thickness, into which region an air channel or air channels openso that—as with a water-jet pump—air is carried into the jet of fluid.

It has been found that a favourable droplet, or particle size, istypically obtained if the narrowest cross-sectional surface area of thenozzle outlet, or outlets, is between about 25 and 500 μm². When thegrooves in the base plate are, for example, 5 μm in depth, it ispossible for the nozzles to be kept to a comparable width and typicallytheir width-/breadth ratio is between about 1:1 and 1:20. Relationshipsoutside these regions are also possible. The skilled person can, ifnecessary, optimize the appropriate nozzle outlet dimensions by carryingout tests as the characteristics of the fluid to be sprayed, as thesurface tension and the viscosity are also relevant to a certain degree.The specific characteristics of the fluid to be sprayed need to beconsidered in particular when that fluid includes an organic solvent oran oil rather than a watery fluid, of the type for which the presentdevice is primarily, but not exclusively, intended.

To exclude the possibility of blockage of the filters, even overlong-term use the filter can also be designed so that it is of zing-bag,meander-like or actuate configuration. Thus, a greater number of throughpassages (of constant size) is formed. In addition, if so desiredinstead of a one or two staged filter it is possible for three-stagedfilters to be provided with respectively narrower through passages. Ineach case, however, it must be ensured that a sufficiently high pressureis available at the nozzle despite the reduction of pressure in thefilter system.

The cross-sectional shape of the nozzle outlet or the sum of thecross-sections of the nozzle outlet can be varied within furtherboundaries. At a given pressure, the cross-section of a slitted nozzleoutlet can be considerably greater than the cross-section of a square orround nozzle outlet, without the droplet spectra being impaired. Thecross-section of the nozzle outlets or the sum of the cross-sections isusually between 5 and 2000 μm², preferably between 20 and 1000 μm² andin particular between 25 and 500 μm². This also applies when two or moreparallel orientated nozzle outlets are provided.

When, also, in particular in the case of very narrow or very flat nozzleopenings, surface edge effects play a large role, the skilled personneeds to take account of the knowledge of the physics concerninghydraulic cross-section in the determination of the arrangement of thenozzle outlets and the choice of the dimensions therefor.

FIG. 12 is a schematic representation of part of another nozzle assemblyin accordance with the invention. FIG. 12 represents a plan view of abase plate 50 in which channels are formed. An inlet 52, which extendsperpendicularly to the plane of the base plate 50, opens into a chamber54. The chamber is connected via one or more filter stages 56 to twinnozzle outlets 58 a and 58 b. The provisional of the perpendicularlyextending inlet enables a compact construction of the nozzle and/ornozzle assembly.

FIG. 13 shows an example of nozzle assembly 60 with an inlet disposedperpendicularly to the connecting surfaces as in FIG. 12.

In the nozzle assembly of FIG. 13, a first plate member 61 has a firstset of two channels 62 in its upper face which debouch at one edge ofthe plate. The resultant apertures at the plate edge form two fluidoutlets which, in the present example, will form two impinging jets offluid angled at about 100 to 120° to one another when fed with fluid.Preferably, the edge of plate 61 is indented at this point to provide arecess in the face of the nozzle assembly within which the two jets offluid can impinge and form the spray of droplets. The lips of the mouthsof the channels 62 where they intersect the edge of the plate 61 aresharply formed and not rounded. The face of plate 61 also carries asecond set of channels 63, which are of smaller cross-section dimensionsthan the first channels 62. These act as the narrow bore portionslinking a fluid inlet 64 cut through plate 61 with the first set ofchannels 62 and serve to filter out solid particles which mightotherwise block the first channels and the fluid outlets. Typically, thesecond channels 63 each have a cross-sectional area which isapproximately 10% or less of the cross-sectional area of each of thefirst channels 62, so as to give a pressure drop of about 0% of theapplied pressure from the flow generating device, for example of from0.2 to 25 bar, across the second channels. Typically, the secondchannels 63 will have at least one cross-sectional dimension which isabout 50% of the corresponding dimension of the first channels. Sincethe channels are typically formed by removing a uniform depth ofmaterial from the surface of the first plate member, the channels willusually have a constant depth and variations in the dimensions or areaof the channels is achieved by varying the width of the channels.

The second set of channels 63 debouch into a plenum chamber 65 cut intothe top face of plate 61. If desired, the chamber 65 can be cut throughthe thickness of plate 61, but it is preferred to form chamber 65 withinthe thickness of plate 61 as shown. Chamber 65 is preferably configuredso that the first channels 62 exit from opposed corners of the chamber65 and a septum 66 of the material of the surface of plate 61 can beretained between the channels 62 to aid changes in direction of flow offluid within chamber 65 and to direct the flow into the first channels62.

A second plate member 70 is shown overlying but detached from the firstplate member 61. When this second plate 70 is secured to the top face ofplate 61 it provides the top faces to the channels 62 and 63 so thatthey form two groups of conduits which form the nozzle outlets 62 andthe filter bores 63.

A third plate member 80 is also shown detached and underlying plate 61.Plate 80 carries a fluid inlet spigot 81 by 5 which the nozzle assemblycan be mounted on the outlet of a pump or other fluid flow generatingdevice (not shown). The spigot 81 has an internal bore 82 which is inregister with the inlet 64 in plate 61 and can form part of the pumpmechanism of the flow generating device as indicated above. The exteriorof spigot 81 can carry screw thread or other means (not shown) by whichthe spigot is secured to the pump or other flow generating means.

The plates 61, 70 and 80 can be formed from any suitable material, forexample a photo-resist glass, ceramic or plastic or a metal, and thefeatures in plate 61 formed by removing material from plate 61 in thedesired locations by a conventional chemical etching process.Alternatively, the features can be formed by removal of material using alaser. Since the features are formed on the exterior of a substantiallyflat member, there is no need for complex machining of components orassembly of sub-components.

The plate members present opposed substantially flat faces to oneanother and can readily be bonded or otherwise secured to one anotherusing any suitable technique, for example by ultra-sonic welding, byadhesion or by clamping them together using a metal surround which iscrimped into position.

In operation, fluid at pressure is delivered to the bore 82 of spigot81, from which is flows through inlet chamber 64 in plate 61, throughthe filter channels 63 to the plenum chamber 65 and thence to the nozzlechannels 62. The fluid exits from the two nozzle channels as jets offluid which impinge on one another to form a spray of fine droplets.

By applying the fluid at a pressure of at least 40 bar to nozzlechannels having a mean diameter of about 10 micrometres, droplets with amean droplet size of less than 10 micrometres were produced.

The nozzle assembly could be manufactured repeatedly to close tolerancesand samples of the nozzle assembly repeatedly performed to give the samedroplets sized spray.

Accordingly, from a further aspect, the present invention provides anozzle and filter assembly characterised in that it comprises:

a. a first plate into which are formed:

1: a first group of channels having one end thereof located at the plateboundary; and

2: a second group of channels of equal or smaller size than said firstgroup; and

b. a second plate that sealingly engages said first plate so the surfaceof said second plate co-operates with the first group of channels insaid first plate to form a first series of fluid outlets and with saidsecond group of channels in said first plate to form a second set offluid conduits having a cross-sectional size equal to or smaller thanthe said fluid outlets, whereby when a fluid is passed through saidsecond group of channels they act as a filter to protect the first setof channels which act as spray forming fluid outlets; and

c. means of connecting said two sets of channels.

Preferably the nozzle assembly is connected to means for supplying firstset of channels with fluid.

In the alternative forms of plate 61 shown in FIGS. 14 to 19, the outletto the channels 62 is modified so that the fluid issues from the outletsas a spray without the need for impingement of two jets of fluid. Thus,in FIG. 14 the outlet 74 to channel 62 is formed as a tortuous bend toinduce secondary flow as the fluid exits the channel 62. To achieve aspray of droplets with a mass median droplet size of about 5micrometres, the fluid outlet by channel 62 is from 2 to 15, preferablyfrom 3 to 8, micrometres square in cross-section.

In the alternative form shown in FIG. 15, a flap 85 is formed at themouth of channel 62 and the edge of plate 61 is cut away in the area 86downstream side of the flap.

In the alternative shown in FIG. 16, the channel 62 is formed with aknife edge entry 91 having a gap 93 of from 4 to 30 micrometres andchannel 62 diverges from that knife edge entry at an included angle 94of from 60 to 150°, preferably from 90 to 120°. In the modificationshown in FIG. 17, the knife edge 101 is formed at the exit to channel 62at the edge of plate 61 and sufficient wall thickness 102 is retainedbetween the edge of the plate and the plenum chamber 65 to ensure therigidity and strength of the knife edge.

In the alternative shown in FIG. 18, the side walls of channel 2 areradially indented to provide a series of projections 111, 112 into theflow of fluid through the channel which induce secondary flow in thefluid as is passes through the mouth of the channel. Typically, with achannel having a maximum mouth cross-sectional dimension of from 5 to 20micrometres, the projections 111 and 112 will be from 3 to 8micrometres.

In the modification of the device of FIG. 13 shown in FIG. 19, a septum120 is formed within the plenum chamber which is separated from the wallof the chamber to provide two passages 121 and 122 which form twoimpinging flows of fluid in a swirl chamber 123 which debouches into asingle outlet channel 62 to provide the secondary flow to form a sprayas the fluid exits the mouth 124 of channel 62.

As indicated above, the depth and width of the channels formed in thefirst plate depend on the application of the nozzle assembly. Forinstance, when the nozzle assembly is used to spray hair sprays, thetotal cross-sectional area of the fluid outlet channels is typically1500 square micrometres. If a single channel is used, this will betypically 40 microns deep by 40 microns wide. To achieve the requiredparticle size of typically 40 micron mass mean diameter using such anozzle assembly, fluid at a pressure of between 30 and 150 bars is used.

If the nozzle assembly is used to spray lung deposited drugs foradministration by inhalation, then typically the total cross sectionalarea of the outlet channel (e.g. 62) will be between 30 and 200 squaremicrometers. If a single outlet channel (e.g. 62) is used, this willtypically be 10 microns deep by 10 microns wide. The operating pressurerequired to achieve a spray with a mass median droplet size of less than6 micrometres will be between 100 and 400 bars.

The nozzle assembly of the invention may be used in other applicationswhere a simple, rugged device is required, for example in fuel injectionsystems for internal combustion engines, where a group of spray nozzleswould typically be used either formed in one plate assembly or using anumber of plate assemblies.

A method of manufacture of a nozzle assembly in accordance with anembodiment of the invention comprising a grooved base plate and anunstructured cover plate will now be described. It will be appreciatedthat the method to be described can readily be modified for producingnozzle assemblies where the cover plate is structured instead of or inaddition to the base plate and/or where an intermediate plate isstructured.

In particular, in the method to be described, the nozzle assemblies aremanufactured using the following steps:

structuring a batch of base plates with grooves;

joining the batch of base and cover plates together; and

separating the individual nozzle assemblies.

The base plate is preferably structured in per se known manner using alight optical lithographic technique in conjunction with anion-supplemented reactive dry etching technique. The heights of thestructures are between 2 and 40 μm, usually between about 3 and 20 μm,preferably between about 4 and 14 μm and particularly between 5 and 7μm. The material used for the base plate is preferably amono-crystalline silicon since this is cheap and available in acondition (i.e. in wafers) in which it is sufficiently flat and paralleland of low surface roughness, and it can be joined to the cover platewithout the additional application of adhesives or other materialsduring the subsequent joining process. In order to produce a pluralityof nozzle assemblies in parallel, a plurality of structure base platesare formed on a wafer of silicon.

It will be appreciated that materials other than silicon can undergostructuring, and these can also be firmly joined to the cover plate inthe subsequent joining process. Such materials are gallium-arsenide ormetals such as aluminium or nickel-cobalt-alloys, for example, which canlikewise be joined properly to a glass plate.

A thin layer of silicon is thermally oxidised on the surface of thewafer W (FIG. 20A) to be structured The oxide layer later acts as a maskwhen the groove finish is etched A light-sensitive plastics layer L2 isthen applied over the layer L1 in a centrifuging process, and allowed tosolidify (FIG. 20B). The groove structures are then transferred to anddeveloped in the plastics layer using optical light by contact copy witha mask M, to a scale of 1:1 (FIG. 20C). In the next step of theprocedure, the plastics structures act as masks for structuring thesilicon oxide layer. The structuring is effected by reactive etchingwith ion beams. During the structuring of the oxide layer, the plasticsmaterial is completely removed (FIG. 20D).

The oxide layer structured in this way then acts as a mask for etchingthe grooves, which may be 5-7 μm in depth, in the silicon. When this isdone, the oxide layer is also slowly removed (FIG. 20E).

At the end of the structuring process, U-shaped or rectangularbox-shaped grooves are formed on the silicon plate, but these groovescan be of any geometric surface shape in the plan view.

With structuring of the base plate, other etching methods can be used toachieve a number of variants to give other shapes of groove which resultin end products with nozzles of varying opening cross-section. Thus, forexample, trapezoidal grooves can be produced by over-etching orunder-etching in the appropriate way. These etched forms can be producedboth by isotropic dry etching methods and by isotropic wet etchingmethods. If anisotropically acting etching methods (both with reactiveion plasma and also with wet chemical media) are used it is possible toproduce nozzles of triangular cross-section from V-shaped grooves inmono-crystalline base plates. The geometric shape of the grooves canalso be altered by combining etching techniques with coating techniques.Virtually any geometric shape can be produced.

After structuring, the silicon plate is cleaned and the rest of thesilicon dioxide is removed by the wet-chemical method. The silicon plateis then joined (FIG. 20F) to a glass plate by anodic bonding (cf. U.S.Pat. No. 3,397,278 of Aug. 13, 1968, Pomerantz, D. I. et al.)

An alkali borosilicate glass such as Pyrex, for example, (#7740 Corning)or Tempax (Schott) is suitable for anodic bonding of silicon and glass.The glass plate is placed on the structured silicon plate and iscontacted with an electrode. The entire composite structure is heated totemperatures of between 200 and 500° C. (preferably to about 450° C.,because up to this temperature the thermal expansion coefficients arestill close to one another and at the same time the alkali ions aresufficiently mobile for a fast bonding process) and a negative voltageof about 1000 V is placed between the silicon plate and the glass plate.Due to this voltage, the positively charged alkali ions move through theglass to the cathode, where they are neutralised. At the point oftransition between the glass and the silicon, a negative spacial chargeis formed in the glass which causes electrostatic drawing together ofthe two surfaces, and also results in a durable chemical bonding beingformed between the glass surface and the silicon surface by means ofoxygen bridging bonds.

In this connection, it is also particularly advantageous to use glass asthe cover material for reasons of quality control, since it is easilypossible to visually detect the efficiency of the bonded connection andalso defects or foreign particles which lead to malfunctions of thecomponent part.

However, other cover materials other than glass can be used. With hightemperature loads it is possible to optimise the thermal expansioncoefficients of the composite member if silicon is used both for thebase plate and for the cover plate. For the joining process, a thinglass layer is applied to the two plates, e.g. in an evaporating orsputtering method, by means of which the bonding process can then becarried out. In this case, a visual inspection can be made usinginfra-red viewing apparatus.

After the bonding process, the composite structure (see FIG. 20G) isdivided into individual units (e.g. squares) by a fast rotating diamondcircular saw, wherein the intake openings and the outlet openings areopened up. If the cross-sectional surface area is very different at theoutlet (as with nozzle-shaped outlet openings, for example), then theseparating cut must be positioned with precision to a few micrometers inorder to obtain a defined nozzle outlet. Such positioning also minimisesthe expanse of the outward flow at the outlet

During the separation stage, particularly high revolutionary speeds areneeded (usually more than 30000 revs/min) in order to avoid expulsion atthe side walls and edges of the nozzle member. Such expulsion couldcause undesirable changes to the cross-section to the geometric shape ofthe outlet.

After dividing them up, the nozzle assemblies are cleaned and are fittedinside appropriate holders.

Although illustrative embodiments of the invention have been describedin detail herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to those preciseembodiments, and that various changes and modifications can be effectedtherein by one skilled in the art without departing from the spirit andscope of the invention as defined by the appended claims.

For example, although various embodiments of the invention are describedseparately herein, it will be appreciated that features from the variousembodiments may be combined as appropriate in yet further embodiments.

What is claimed is:
 1. A nozzle assembly for atomizing a flow of fluidsupplied at a pressure into fine droplets, comprising: a first memberhaving a first surface, said first surface having a plurality of groovesformed therein; a second member having a second surface, requiring saidfirst and said second surfaces to be joined together to form a pluralityof passageways; and a plurality of nozzle outlets disposed at one end ofsaid plurality of passageways, wherein said plurality of nozzle outletsare configured to discharge a plurality of fluid jets, so that said jetsimpinge on one another to thereby atomize the flow of fluid.
 2. Thenozzle of claim 1, further comprising a filter disposed at one end ofsaid plurality of passageways.
 3. The nozzle of claim 1, wherein saidplurality of passageways are substantially rectangular in cross-section.4. The nozzle of claim 1, wherein said plurality of jets impinge at anangle of approximately 60 degrees to approximately 150 degrees.
 5. Thenozzle of claim 1, wherein said plurality of jets impinge at an angle ofapproximately 90 degrees to approximately 120 degrees.
 6. The nozzle ofclaim 1, herein said plurality of jets impinge at an angle ofapproximately 90 degrees.
 7. The nozzle of claim 1, further comprising aplenum chamber formed in said first member, wherein said plenum chamberis in fluid communication with said plurality of passageways.
 8. Thenozzle of claim 1, wherein said plurality of passageways aresubstantially parallel to each other.
 9. The nozzle of claim 1, furthercomprising a fluid inlet means.
 10. The nozzle of claim 9, wherein saidfluid inlet means is disposed substantially at a right angle to saidfirst member.
 11. The nozzle of claim 10, further comprising a fluidinlet chamber into which fluid is received from said fluid inlet means,wherein said fluid inlet chamber is in fluid communication with saidplurality of passageways.
 12. The nozzle of claim 1, wherein saidplurality of passageways are configured to receive a flow of fluidsupplied at a pressure of at least 50 bar.
 13. The nozzle of claim 1,wherein said plurality of passageways are configured to receive a flowof fluid supplied at a pressure of approximately 50 bar to approximately400 bar.
 14. The nozzle of claim 1, wherein said plurality ofpassageways are configured to impose a pressure drop of approximately0.2 bar to approximately 25 bar to the flow of fluid.
 15. The nozzle ofclaim 1, wherein said plurality of nozzle outlets have a totalcross-sectional area of approximately 25 to approximately 500 squaremicrometers.
 16. The nozzle of claim 1, wherein said plurality of nozzleoutlets have a total cross-sectional area of approximately 30 toapproximately 200 square micrometers.
 17. The nozzle of claim 1, whereinsaid first member comprises silicon.
 18. The nozzle of claim 17, whereinsaid first member further comprises glass.
 19. The nozzle of claim 1,wherein said second member comprises silicon.
 20. The nozzle of claim19, wherein said second member further comprises glass.